How to get to Jones beach by train?

Is there a train i can get at the MTA LIRR in Valley Stream to Jones beach to get to the Nikon at Jones Beach theater?

Sort of. The NICE N88 bus runs from the Freeport station to Jones Beach, and has schedules for concerts, see the link below. Unfortunately, although the Freeport trains go through Valley Stream, almost none of them stop there, so you have to change at Lynbrook or even go back to Jamaica.

You're probably better off taking the NICE N4 bus to Freeport and connecting to the N88 there.